The present invention relates to an ink jet recording apparatus for ejecting ink droplets toward a recording medium by causing an electrostatic force to act on ink containing charged colorant particles, and a method of controlling the same.
As for a recording method with which ink droplets each containing colorant particles are ejected to record an image on a recording medium, for example, there is known an electrostatic ink jet recording system in which ejection of ink droplets is controlled by utilizing an electrostatic force through application of a predetermined voltage (drive voltage) corresponding to image data to an ejection electrode of an ink jet head, thereby recording an image corresponding to the image data on a recording medium by using ink containing charged colorant particles.
In a recording apparatus using the electrostatic ink jet recording system, since an electrostatic force acting on ink changes when a distance (gap) between an ink jet head and a recording medium, a resistance of the recording medium, physical properties of the ink or the like change, an ejection state of ink droplets changes accordingly. As a result, there is encountered a problem that an image of high image quality cannot be stably recorded since a change occurs in the recorded image.
For coping with such a problem, in order to realize an electrostatic ink jet recording apparatus capable of stabilizing recording quality by maintaining a stable ejection electric field strength, JP 3056109 B discloses a printing head gap regulating mechanism in which a gap defined between an ejection electrode and a recording medium, and a gap defined between the ejection electrode and a counter electrode for supporting the recording medium are measured, an electric field strength in the ejection electrode after insertion of the recording medium is calculated based on the measured gaps, and gap regulating means regulates a printing head gap so that conditions for achieving stable ejection are obtained.
In addition, in order to stabilize an electric field for causing ink to fly (hereinafter referred to as “ink-flying electric field”) to enable an image of high image quality to be printed (recorded) on various recording media even when the recording media are different in thickness and material from one another, JP 11-245390 A discloses an ink jet recording apparatus in which a distance between an ejection electrode and a recording medium and a kind of recording medium are detected, and conditions for the application voltage to an electrode for generating an ink-flying electric field are controlled in correspondence to the detection results.
Moreover, in order to realize an electrostatic ink jet printer capable of carrying out a proper printing operation without being influenced by a conductivity of ink, JP 2001-239670 A discloses an ink jet printer in which the conductivity of ink is measured, and output time and a voltage value of a pulse signal of an ejection voltage to be applied to an electrode are corrected based on a measured value.
However, in the ink jet recording apparatus, the gap defined between the ink jet head and the recording medium, the resistance of the recording medium, and the physical properties of the ink complexly change.
The printing head gap regulating mechanism disclosed in JP 3056109 B is regarded as being able to correct a change in ejection state of the ink droplets which is caused due to the distance (gap) between the ink jet head and the recording medium. However, if the resistance of the recording medium and the physical properties of the ink change, the ejection state of the ink droplets changes accordingly.
In addition, the ink jet recording apparatus disclosed in JP 11-245390 A is also regarded as being able to correct a change in ejection state of the ink droplets which is caused due to the distance (gap) between the ink jet head and the recording medium and the resistance of the recording medium. However, if the physical properties of the ink change, the ejection state of the ink droplets changes accordingly.
Moreover, the ink jet printer disclosed in JP 2001-239670 A is regarded as being able to correct a change in ejection state of the ink droplets which is caused by a change in physical properties of the ink. However, if the gap defined between the ink jet head and the recording medium and the resistance of the recording medium change, the ejection state of the ink droplets changes accordingly.
Thus, in the ink jet recording apparatuses disclosed in JP 3056109 B, JP 11-245390 A, and JP 2001-239670 A, if a plurality of factors simultaneously change, the ejecting conditions can not be corrected in correspondence to such changes, and the ejection state of the ink droplets thus changes. Thus, there is encountered a problem that since the ejection state of the ink droplets can not be fixed, an image of high image quality can not be stably formed.